 After this loss, Iskandar Muda launched only two more sea expeditions, in 1630/1 and 1634, both to suppress revolts in Pahang.His sultanate maintained control over northern Sumatra, but was never able to gain supremacy in the strait or expand the empire to the rich pepper-producing region of Lampung on the southern part of the island, which was under the control of the sultanate of Banten.The economic foundations of the sultanate was the spice trade, especially in pepper.